This invention relates to a brush head for a toothbrush, which includes a hand-piece with a drive mechanism for the brush head, with an in particular disk- or plate-shaped bristle support which carries an array of bristles, is mounted for movement on a brush head support and includes connecting elements for coupling to the drive mechanism in the handpiece of the toothbrush, said bristle support being divided into several bristle support segments movable relative to each other, and with driving elements changing the position of the bristle support segments relative to each other in dependence upon the position of the entire bristle support.
In electric toothbrushes increased importance has been recently attached to the cleaning of interproximal spaces and periodontal pockets. Attempts are made to work the bristles into the interproximal spaces to remove plaque buildup there. However, the length and the fixed securing of the bristles set a certain limit to these attempts. From EP 0 835 081 B1 a brush section for an electric toothbrush is known, which includes a bristle support which is rotary about an axis of rotation perpendicular to the brush longitudinal direction and is adapted to be driven in an oscillatory rotary movement. Arranged in several rings on the bristle support are bristle tufts, some of the bristle tufts being provided on the outermost bristle tuft ring in diametrically opposed segments, said tufts protruding beyond the remainder of the bristle tufts and being of increased stiffness. These tufts, referred to as power tips, are intended to penetrate in the interproximal spaces to perform a particularly thorough cleaning function there. This prior known arrangement is however capable of further improvement. Owing to the oscillation of the bristle support the power tips perform a wiping action into and out of the interproximal spaces, without however optimally reaching the respective interproximal space due to the motion curve resulting in the process, because it is first necessary to wipe over the gums before the interproximal space can be entered. Furthermore, the penetration depth of the power tips in the inter-proximal space amounts to no more than the amount of protrusion over the remainder of the bristles.
From U.S. Pat. No. 5,732,433 a brush head of an electric toothbrush is known, which includes another bristle support with supplementary bristles in addition to the main bristle support driven in an oscillatory rotational pattern about an axis of rotation normal to the brush longitudinal direction and carrying an approximately circular array of bristles. This additional bristle support is constructed as a component separate from the main bristle support and sits directly on a drive shaft extending in the interior of the brush head support and driving also the main bristle support. The additional bristles are driven to oscillate in a rotary manner about the drive axis, that is, about the longitudinal axis of the brush, and are to sweep out the interproximal spaces. Apart from the fact that this separate drive of the supplementary bristle array is relatively complex, the aforementioned problem is not eliminated, that is, the extended additional bristles are unable to penetrate between adjacent teeth sufficiently deeply.
In this context, an improvement is achievable by enabling the power tips to penetrate in the interproximal space in a pulsing motion. EP 1 093 770 A2 proposes a brush head of the prior-art type in which the essentially disk-shaped bristle support, which is adapted to be driven in rotary oscillatory manner, is divided into several bristle support segments that are movable relative to each other. The power tips are arranged on a rocker which is mounted for rocking motion about a rocker axis extending in a direction transverse to the axis of rotation of the bristle support and forms opposite segments of the bristle support, so that by rocking up and down corresponding pulsing or poking motions of the power tips can be achieved. In this arrangement the rocking motions are produced by a crank mechanism mounted on the drive shaft provided in the interior of the brush tube to effect the oscillatory rotational motion of the bristle support. Accordingly, the rocking motion is coupled to the oscillatory rotational motion of the bristle support, that is, the rocker-like bristle support segments are moved in dependence upon the rotary position of the entire bristle support. Due to the arrangement of the power tips on a rocker, however, only those power tips that are arranged on one side will enter the interproximal space at a time, because the opposite power tips are withdrawn according to the principle of a seesaw. Moreover, the drive mechanism producing the rocking motion is relatively complex in addition to necessitating a special type of bristle support drive, namely a drive shaft rotating or oscillating about its longitudinal axis.